Human and animal surgery frequently requires the grasping, manipulating or cutting of tissue or other organic living matter at some distance from the surgeon's hands. In such cases endoscopic surgical methods are commonly employed that make it possible for skillful and precise surgery to be conducted despite the fact that the surgical site is a substantial number of inches from the point of initial incision in the person or animal being operated on. Endoscopic surgical procedures encompass both arthroscopic and laparoscopic surgery techniques. In endoscopic surgery, small incisions are made in the exterior surface of the person or animal being operated on, and the work being performed is observed by the operating surgeon by means of a an optical device known as an endoscope which is inserted into the person or animal through a small incision. Endoscopic surgical techniques are displacing conventional open surgical techniques for many procedures, and hence there is a need for improved instruments for conducting such procedures.
A wide variety of surgical instruments have been devised for use in arthroscopic and laparoscopic surgical procedures, including instruments such as graspers, forceps and scissors for use in grasping, cutting or otherwise remotely manipulating bodily tissue and other matter during surgery.
A typical instrument employed in endoscopic surgery has a pair of articulated jaws, and a handle mechanism comprising two members, one movable with respect to the other, which can conveniently be manipulated so as to cause the jaws to open and close. Serrations, blades, cutting edges, or other features (depending upon the use for which the tool is intended) enable the jaws to perform various surgical functions, such as grasping or cutting. The articulated jaws are located at the distal end of a relatively long extension of the handle mechanism. The length of the extension is determined by the depth of the surgical site, while its cross-sectional dimensions are established by the maximum permissible incision size.
Many ingenious linkages have been devised for converting the surgeon's manual efforts at the handle end of the instrument into opening and closing of the tool's jaws. Most commonly, the surgical tool comprises a stationary handle member rigidly joined to a hollow outer shaft and a movable handle member pivotally attached to a coaxial inner shaft in the form of a tube or solid rod that is capable of reciprocal axial movement relative to the outer shaft, with the jaws being operatively coupled between the outer hollow shaft and the inner shaft member so as to open and close in accordance with relative axial movement of the outer and inner shafts. When the surgeon squeezes the stationary and movable handle members together, the outer and inner shafts coact in such a way as to make the jaws close. When the surgeon spreads the stationary and movable handle members apart, the motions are reversed and the jaws open. Publications illustrating the prior art include U.S. Pat. No. 3,404,677 and the prior art cited therein, as well as the following references: U.S. Pat. Nos. 4,836,205; 4,258,716; 4,084,594; 4,393,872; 5,026,375; 4,712,545; and 5,026,370.